转载：approxPolyDP函数

本文转载http://blog.csdn.net/qq_18343569/article/details/47999257

1、approxPolyDP函数

函数的作用：

对图像轮廓点进行多边形拟合

2、函数的调用形式

C++: void approxPolyDP(InputArray curve, OutputArray approxCurve, double epsilon, bool closed)

参数详解;

InputArray curve:一般是由图像的轮廓点组成的点集

OutputArray approxCurve：表示输出的多边形点集

double epsilon：主要表示输出的精度，就是另个轮廓点之间最大距离数，5,6,7，，8，，,,，

bool closed：表示输出的多边形是否封闭

3、OPENCV代码

 #include "opencv2/highgui/highgui.hpp"
 #include "opencv2/imgproc/imgproc.hpp"
 #include <iostream>
 #include <stdio.h>
 #include <stdlib.h>

 using namespace cv;
 using namespace std;

 Mat src; Mat src_gray;
 int thresh = ;
 int max_thresh = ;
 RNG rng();

 /// Function header
 void thresh_callback(int, void*);

 /** @function main */
 int main(int argc, char** argv)
 {
     /// 加载源图像
     src = imread("D:6.jpg", );

     /// 转成灰度图并进行模糊降噪
     cvtColor(src, src_gray, CV_BGR2GRAY);
     blur(src_gray, src_gray, Size(, ));

     /// 创建窗体
     char* source_window = "Source";
     namedWindow(source_window, CV_WINDOW_AUTOSIZE);
     imshow(source_window, src);

     createTrackbar(" Threshold:", "Source", &thresh, max_thresh, thresh_callback);
     thresh_callback(, );

     waitKey();
     return();
 }

 /** @function thresh_callback */
 void thresh_callback(int, void*)
 {
     Mat src_copy = src.clone();
     Mat threshold_output;
     vector<vector<Point> > contours;
     vector<Vec4i> hierarchy;

     /// 对图像进行二值化
     threshold(src_gray, threshold_output, thresh, , THRESH_BINARY);

     /// 寻找轮廓
     findContours(threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(, ));
     /*Mat drawing = Mat::zeros(threshold_output.size(), CV_8UC3);*/

     /* 对每个轮廓计算其凸包*/
     vector<vector<Point> >poly(contours.size());
     for (int i = ; i < contours.size(); i++)
     {
         approxPolyDP(Mat(contours[i]), poly[i], ,true);
     }

     /* 绘出轮廓及其凸包*/
     Mat drawing = Mat::zeros(threshold_output.size(), CV_8UC3);
     for (int i = ; i< contours.size(); i++)
     {
         Scalar color = Scalar(rng.uniform(, ), rng.uniform(, ), rng.uniform(, ));
         drawContours(drawing, contours, i, color, , , vector<Vec4i>(), , Point());
         drawContours(drawing, poly, i, color, , , vector<Vec4i>(), , Point());
     }
     /*vector<Point> poly;
     approxPolyDP(Mat(contours[3]), poly, 5, false);
     vector<Point>::const_iterator itp = poly.begin();
     while (itp != (poly.end() - 2))
     {
         line(drawing, *itp, *(itp + 1), Scalar(255), 2);
         ++itp;
     }
     line(drawing, *itp, *(poly.begin()), Scalar(255), 2);*/
     /// 把结果显示在窗体
     namedWindow("Hull demo", CV_WINDOW_AUTOSIZE);
     imshow("Hull demo", drawing);
 }